This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A129574 #11 Feb 01 2025 08:50:31
%S A129574 1,2,3,3,3,4,4,3,4,5,4,4,4,4,6,5,3,5,5,4,6,6,4,4,5,5,6,6,4,6,6,3,5,6,
%T A129574 6,7,5,4,6,6,4,6,6,4,8,8,4,4,5,6,7,6,4,6,8,6,6,6,4,6,6,4,8,7,5,8,6,4,
%U A129574 6,8,6,5,5,4,8,8,6,8,6,4,7,7,4,6,8,6,6,6,4,8
%N A129574 Number of odd divisors of n plus the number of odd divisors of n - 1.
%H A129574 Andrew Howroyd, <a href="/A129574/b129574.txt">Table of n, a(n) for n = 1..1000</a>
%F A129574 a(n) = A001227(n) + A001227(n-1). - _Andrew Howroyd_, Aug 10 2018
%e A129574 a(4) = 3 = sum of row 4 of triangle A129573: (1 + 0 + 1 + 1).
%t A129574 Join[{1},Table[Total[Mod[Divisors[n],2]]+Total[Mod[Divisors[n-1],2]],{n,2,90}]] (* _James C. McMahon_, Jan 31 2025 *)
%o A129574 (PARI) a(n)=numdiv(n >> valuation(n,2)) + if(n > 1, numdiv((n-1) >> valuation(n-1,2))) \\ _Andrew Howroyd_, Aug 10 2018
%Y A129574 Row sums of A129573.
%Y A129574 Cf. A001227.
%K A129574 nonn
%O A129574 1,2
%A A129574 _Gary W. Adamson_, Apr 22 2007
%E A129574 Name changed and terms a(11) and beyond from _Andrew Howroyd_, Aug 10 2018